I am trying to place new T-bars on my sons Razor Pro scooter. The new bars are smooth on the inside and the old ones are threaded. We still have the threaded fork end on his scooter that the new bars slide over. The clamp is the standard clamp for his Razor Pro. Once installed, any moderate force pulls the bars off. The threaded ones don't obviously. How do we eliminate this problem? Does he need a new clamp? Any suggestions would be helpful. Thanks